Plasticizers are compounds or mixtures of compounds that are incorporated into a polymer resin to increase the softness, flexibility, workability, or distensibility of the polymer resin. Common plasticizer includes phthalates, in particular, ortho-phthalates. In recent years, di-2-ethylhexyl phthalate (DEHP or DOP) and shorter alkyl chain length phthalate esters have been restricted in certain applications or are the subject of increased scrutiny due to their toxicological properties and the world wide environmental regularity. Thus, it must be at least considered that alternative plasticizers will be required. For these and most other uses of plasticized polymer systems, high molecular weight phthalates like diisodecyl phthalate (DIDP) and also the plasticizer free of ortho-phthalte such as terephthalic esters like dioctyl terephthalate (DOTP), cyclohexane acid ester like diisononyl 1,2-cyclohexanedicarboxylate (DINCH) have been developed.
U.S. Pat. No. 2,628,207 discloses a composition comprising 100 parts of a resinous copolymer of about 95% vinyl chloride and about 5% vinyl acetate, and 5-100 parts of a DOTP.
US2010/0305250 discloses C7-C12 secondary alcohol esters of cyclohexanecarboxylic acids as plasticizers for polyvinyl chloride (PVC) and other plasticizable polymers.
WO2008/140177 discloses a plasticizer composition comprising at least three different terephthalic acid compounds.
US2013/0310472A1 discloses a foamable composition containing a polymer selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, polyvinyl butyrate, polyalkyl(meth)acrylate and copolymers thereof, a foam former and/or foam stabilizer and di-2-ethylhexyl terephthalate as plasticizer.
US2003/0014948A1 describes the plasticized polyvinyl chloride (PVC) wherein plasticizers comprising dioctyl terephthalate and dioctyl adipate.
US2014/0162045A1 describes a polyvinyl chloride (PVC) article, comprising a PVC resin, a primary plasticizer and a metal-carboxylate acid scavenger. The PVC article further comprises a secondary plasticizer. The primary and secondary plasticizer are selected from the group consisting of phthalates, terephthalate, epoxidized vegetable oils, trimellitates, polyesters, phosphates, citrates, benzoates, sulphonates, and adipates.
Despite all the above-mentioned work, an efficient plasticizer, which can enhance processability, plasticizer absorption speed, weight stability at high temperature, electrical volume resistivity and also reduce defect point of the plasticized polymer at comparable strength, migration and heat stability properties, is still being sought.
It has surprisingly been found that this object can be achieved by a plasticizer composition comprising a terephthalic acid di-ester and an ester having the following formula (I):
wherein R1 and R2 are the same or different and represent a straight chain, branched or cyclic hydrocarbyl group.